曝光台 注意防骗
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3. select a suitable precautionary landing area. In the event that you are unable to re-engage the engine a landing would become necessary; and
4. verbal warning. A warning of your intentions to the crew, in this case, your instructor, should preface all practice autorotations. The phrase “Practice engine failure” clearly describes the manoeuvre that you are about to conduct.
A memory aid for the checks is as follows:
H - Height - sufficient for exercise;
A - Area - good for landing if required;
S - Security - straps, no loose articles;
E - Engine - Temperatures and pressures; and
L - Lookout - Good look around especially below and check the wind velocity.
Once you have completed the pre-entry checks, you may now set up the helicopter for the entry to autorotation. Select an altitude that will provide sufficient height so that you will not be rushed, and that will give you plenty of time to experience the flying characteristics of the helicopter in autorotation. For the purpose of this exercise, establish the helicopter straight and level prior to the point where you will lower the collective; the airspeed should be at normal cruise. While it is not always possible to perform this manoeuvre into wind, during the early stages of autorotational training you should ensure that you are flying into the wind, and, of course, that the area below is clear.
NOTE: The policy of most schools is that they do NOT let students perform any autorotational exercise when solo.
ENTRY
To enter autorotational descent first lower the collective fully; to ensure that the rotor RPM does not exceed the manufacturers’ limits; smoothly roll off the throttle. It is important to make these movements smooth, so that you can anticipate the requirement for aft cyclic to prevent any nose down pitching moment, and at the same time, for a pedal adjustment to keep straight. The rotor RPM and engine RPM needles should be split at this point.
The helicopter will now begin to descend. Select an attitude with cyclic to decrease the airspeed from cruise to the manufacturer’s minimum rate of descent speed. You will see that just as in powered flight, the cyclic controls the heading and the airspeed. The collective controls rotor RPM in autorotation, raise it to reduce RRPM, lower it to increase RRPM. You must also maintain the helicopter in coordinated flight with the pedals. Flying with the ball out of centre is aerodynamically inefficient and will adversely affect the airspeed and the glide distance.
Figure 7-1: Autorotation Entry To Overshoot
TURNING
Your instructor will have you carry out some turning manoeuvres. Particularly note that both the RRPM and the rate of descent increase, and that it may be necessary to raise the collective slightly to prevent a possible rotor overspeed. Later on you will learn how to use these two facts to vary your range in autorotations depending on the existing conditions. In any case you will want to roll off any bank, as soon as practical, to reduce the rate of descent and to prepare for the flare and landing. However, in this exercise you will be practising the overshoot while later lessons will deal with the autorotative flare and landing. During the descent you must check the temperatures and pressures are in the normal operating range and that the engine is still operating and will be available for you to commence your overshoot.
OVERSHOOTING
To make an overshoot from the autorotational descent, smoothly increase the throttle to rejoin the needles within the correct operating range. Be prepared to raise the collective as necessary to prevent any tendency for the rotor to overspeed. Once the needles are matched, raise the collective to set climb power and at the same time adjust the cyclic to achieve the best rate of climb. Anticipate the requirement for pedal to maintain the helicopter in co-ordinated flight throughout the transition from autorotational descent to powered flight. Once you have established a stabilized climb perform a post-takeoff check, ensuring all temperatures and pressures are in the normal operating range. This is important because you have been operating the engine at idle while conducting your autorotations.
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